The director of public prosecutions has vigorously defended the decision to prosecute a rape complainant who went on to kill herself days before her trial for perverting the course of justice.

Alison Saunders, the DPP, has carried out an examination into the case of Eleanor de Freitas, a 23-year-old woman who took her own life when the man she alleged had raped her pursued a private prosecution against her, which was taken over by the Crown Prosecution Service.

De Freitas, who had bipolar disorder and had been sectioned in a mental health unit in the past, killed herself in April this year, three days before the trial was due to begin at Southwark crown court.

Saunders said she had expressed her personal and heartfelt sympathies to the woman’s family but defended the actions of the CPS, saying the evidential and public interest tests were both met, and the case against the young woman was strong.

Saunders – who met De Freitas’s father, David, to explain her decision – described the case as unique and tragic. It involved careful consideration because De Freitas had mental health problems, Saunders said, but also because it was the subject of a private prosecution without a full police investigation.

She said when her lawyers were asked to intervene in the private prosecution brought by the man at the centre of the rape claims, they found the alleged perpetrator had gathered strong evidence.

“When we receive a request to intervene, as we did in this case, we must consider that request and apply the same test … as we would to any other prosecution,” Saunders said.

“The evidence in this case was strong and having considered it in light of all of our knowledge and guidance on prosecuting sexual offences and allegedly false rape claims, it is clear there was sufficient evidence for a realistic prospect of conviction for perverting the course of justice.

“This evidence included text messages and CCTV footage that directly contradicted the account Ms De Freitas gave to the police. This was not an assumption based on her behaviour or actions which fall into myths or stereotypes about how alleged rape victims should behave.”

Saunders went on: “It was on this basis that we concluded there was a realistic prospect of proving that the rape allegation made by Ms De Freitas was false, and there was also a strong public interest in prosecuting due to the seriousness of the alleged offence which was maintained by the defendant (De Freitas) for some time and which led to the arrest of an individual.”

Saunders said she was also satisfied that her lawyers had taken the necessary steps to assure themselves De Freitas’s mental health problems had been properly considered. She said medical experts provided by De Freitas’s legal team found that she was fit to stand trial.

“We do not take on these kind of prosecutions lightly, but the medical evidence provided to us could not justify dropping such a serious case,” she said.

The case against De Freitas was pursued without the support of the officers who investigated the original rape complaint.

Saunders said the police were not in a position to take a view on the case for perverting the course of justice, as they “never undertook an investigation into the alleged perverting the course of justice nor did they consider all the material provided to us by the private prosecution”.

She blamed the CPS’s failure to disclose material to De Freitas’s team on the police failing to support the prosecution.

The Guardian can reveal it was only when the CPS met with a senior police officer, assistant commissioner Martin Hewitt – who overruled his specialist sex crime investigators – that the police began to co-operate with the prosecution against De Freitas.

De Freitas reported an alleged rape to the police in January 2013, a few days after the alleged incident in which she said she had been drugged then raped. Specialist sex crime detectives investigated, and the alleged perpetrator was arrested, but they later told De Freitas they could not proceed as there was not a realistic chance of a successful conviction, partly due to inconsistencies in her account.

David De Freitas said his daughter accepted the decision. But the alleged perpetrator pursued a private prosecution through a firm of lawyers. Some months later the CPS took over the case. The trial against De Freitas was due to open on 7 April this year. On 4 April she killed herself.

Victim Support, Justice for Women and the charity Inquest have raised concerns about the decision to prosecute De Freitas. But Saunders said if a private prosecution in such cases was found to meet both evidential and public interest tests, as the De Freitas case did, it should only be left with a private prosecutor in exceptional cases.

David de Freitas said: “We are disappointed that even in light of the subsequent tragedy, the DPP is digging her heels in and standing by this prosecution. We are disappointed that she does not acknowledge there are lessons to be learnt from what happened to Eleanor.

“The failure to take on lessons has disastrous implications for trust in the Crown Prosecution Service if they are concerned about encouraging rape victims to come forward.

“I spoke out in the first place because I was concerned that other vulnerable women and their families should not go through what we have been through.”